nv2021_flags NVIDIA HPC SDK Compilers 2021. Optimization, Compiler, and Other flags for use by SPEChpc

Compilers: PGI Accelerator Fortran/C/C++ Server

Operating systems: Linux

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The OpenMPI C++ driver configured for use with the NVIDIA HPC C++ compiler (nvc++).

]]> mpic++ The OpenMPI C driver configured for use with the NVIDIA HPC C compiler (nvc).

]]> pgcc The OpenMPI Fortran driver configured for use with the NVIDIA HPC Fortran compiler (nvfortran).

]]> pgfortran Disable warning messages.

]]> -w Don't include Fortran main program object module.

]]> -Mnomain Use C++ 17 language features.

]]> --c++17 Use C++ 14 language features.

]]> --c++14 Chooses generally optimal flags for the target platform.

]]> -fast Disable C++ exception handling support.

]]> --no_exceptions Disable C++ run time type information support.

]]> --no_rtti Generate zero-overhead C++ exception handlers.

]]> Disable loop autoparallelization within a acc parallel region.

]]> -acc=noautopar Enable OpenACC directives targeting NVIDIA GPUs

]]> -acc=gpu Enable OpenACC directives targeting multicore CPUs.

]]> -acc=multicore Enable OpenACC directives.

]]> -acc Inline functions declared with the inline keyword.

]]> -Mautoinline Disable inlining of functions declared with the inline keyword. <Default>

]]> -Mnoautoinline Align "unconstrained" data objects of size greater than or equal to 16 bytes on cache-line boundaries. An "unconstrained" object is a variable or array that is not a member of an aggregate structure or common block, is not allocatable, and is not an automatic array. On by default on 64-bit Linux systems.

]]> -Mcache_align Align doubles on double alignment boundaries

]]> -Mdalign Do not align doubles on double alignment boundaries. <Default>

]]> -Mnodalign Swap byte-order for unformatted input/output.

]]> -Mbyteswapio Set SSE to flush-to-zero mode; if a floating-point underflow occurs, the value is set to zero.

]]> -Mflushz Generate code to set up a stack frame. <Default>

]]> -Mframe Eliminates operations that set up a true stack frame pointer for every function. With this option enabled, you cannot perform a traceback on the generated code and you cannot access local variables.

]]> -Mnoframe SPEChpc flags file rule used to split an optimization flag containing sub-options into multiple flag descriptions. Please refer to the flag file rule of the various sub-options for the actual flag description. Instructs the compiler to use relaxed precision in the calculation of floating-point reciprocal square root (1/sqrt). Can result in improved performance at the expense of numerical accuracy.

]]> -Mfprelaxed=rsqrt Instructs the compiler to use relaxed precision in the calculation of floating-point square root. Can result in improved performance at the expense of numerical accuracy.

]]> -Mfprelaxed=sqrt Instructs the compiler to use relaxed precision in the calculation of floating-point division. Can result in improved performance at the expense of numerical accuracy.

]]> -Mfprelaxed=div Instructs the compiler to use relaxed precision for intrinsics. Can result in improved performance at the expense of numerical accuracy.

]]> -Mfprelaxed=div Instructs the compiler to allow floating-point expression reordering, including factoring. Can result in improved performance at the expense of numerical accuracy.

]]> -Mfprelaxed=order Instructs the compiler to use relaxed precision in the calculation of some intrinsic functions. Can result in improved performance at the expense of numerical accuracy.

]]> -Mfprelaxed Instructs the compiler to extend the sign bit that is set as a result of an object's conversion from one data type to an object of a larger signed data type.

]]> -Msignextend The numerical method used when computing the residual iterations of a vectorized (SIMD) loop may be different than used in the vectorized loop. Using this option may lead for fast but less numerically consistent results.

]]> -Mnouniform Allow expression re-association; specifying this sub-option can increase opportunities for loop-carried redundancy elimination.

]]> -Mlre=assoc Disable expression re-association.

]]> -Mlre=noassoc Enables loop-carried redundancy elimination, an optimization that can reduce the number of arithmetic operations and memory references in loops.

]]> -Mlre Disable loop-carried redundancy elimination. <Default>

]]> -Mnolre Print compiler feedback messages for acceleration.

]]> -Minfo=accel Print compiler feedback messages for OpenMP.

]]> -Minfo=accel Print compiler feedback messages.

]]> -Minfo SPEChpc flags file rule used to split an optimization flag containing sub-options into multiple flag descriptions. Please refer to the flag file rule of the various sub-options for the actual flag description. Instructs the inliner to inline the functions within the library filename.ext.

]]> -Minline=lib:filename.ext Instructs the inliner to inline all eligible functions except $1, a function in the source text. Multiple functions can be listed, comma-separated.

]]> -Minline=except:func foo Instructs the inliner to inline function func.

]]> -Minline=name:func Allows inlining in Fortran even when array shapes do not match.

]]> -Minline=reshape Instructs the inliner to inline functions with $1 or fewer statements where $1 is a supplied constant value.

]]> N -Minline=size:n Limit inlining to total size of n.

]]> N -Minline=totalsize:n Inline only functions smaller than n.

]]> N -Minline=maxsize:n Always inline functions smaller than n.

]]> N -Minline=smallsize:n Instructs the inliner to perform $1 levels of inlining where $1 is a supplied constant value. If no value is suppiled, then the default value of 2 is used.

]]> N -Minline=levels:4 Instructs the inliner to perform 1 level of inlining.

]]> -Minline Place automatic arrays on the stack.

]]> -Mstack_arrays SPEChpc flags file rule used to split an optimization flag containing sub-options into multiple flag descriptions. Please refer to the flag file rule of the various sub-options for the actual flag description. Assume all pointers and arrays are independent and safe for aggressive optimizations, and in particular that no pointers or arrays overlap of conflict with each other.

]]> -Msafeptr=all Instructs the compiler that arrays and pointers are treated with the same copyin and copyout semantics as Fortran dummy arguments.

]]> -Msafeptr=arg Instructs the compiler that local pointers and arrays do not overlap or conflict with each other and are independent.

]]> -Msafeptr=auto Instructs the compiler that local pointers and arrays do not overlap or conflict with each other and are independent.

]]> -Msafeptr=local Instructs the compiler that static pointers and arrays do not overlap or conflict with each other and are independent.

]]> -Msafeptr=static Instructs the compiler that global or external pointers and arrays do not overlap or conflict with each other and are independent.

]]> -Msafeptr=global Instructs the C/C++ compiler to override data dependencies between pointers of a given storage class.

]]> -Msafeptr ACCEL flags file rule used to split an optimization flag containing sub-options into multiple flag descriptions. Please refer to the flag file rule of the various sub-options for the actual flag description. Instructs the compiler to completely unroll loops with a constant loop count of less than or equal to $1 where $1 is a supplied constant value. If no constant value is given, then a default of 4 is used. A value of 1 inhibits the complete unrolling of loops with constant loop counts.

]]> N -Munroll=c:1 "-Munroll=n:n" instructs the compiler to unroll loops $1 times where $1 is a supplied constant value. If no constant value is given, then a default of 4 is used.

]]> N -Munroll=n:n "-Munroll=m:n" instructs the compiler to unroll loops with multiple blocks $1 times where $1 is a supplied constant value. If no constant value is given, then a default of 4 is used.

]]> N -Munroll=m:n Instructs the compiler to unroll loops with multiple blocks using the default value of 4 times

]]> -Munroll=m Invokes the loop unroller.

]]> -Munroll Disable loop unrolling. <Default>

]]> -Mnounroll Don't check dependence relations for vector or parallel code.

]]> Treat plain char as signed.

]]> -Mschar Treat plain char as unsigned.

]]> -Muchar Disable an optional post-pass instruction scheduling. <Default>

]]> -Mnosmart SPEChpc flags file rule used to split an optimization flag containing sub-options into multiple flag descriptions. Please refer to the flag file rule of the various sub-options for the actual flag description. Disable automatic vector pipelining. <Default>

]]> -Mnovect Instructs the vectorizer to generate alternate code for vectorized loops when appropriate. For each vectorized loop the compiler decides whether to generate altcode and what type or types to generate, which may be any or all of:

The compiler also determines suitable loop count and array alignment conditions for executing the altcode.

]]> -Mvect=altcode Disables alternate code generation for vectorized loops.

]]> -Mvect=noaltcode Instructs the vectorizer to enable certain associativity conversions that can change the results of a computations due to roundoff error. A typical optimization is to change an arithmetic operation to an arithmetic opteration that is mathmatically correct, but can be computationally different, due to round-off error.

]]> -Mvect=assoc Instructs the vectorizer to disable associativity conversions.

]]> -Mvect=noassoc Instructs the vectorizer, when performing cache tiling optimizations, to assume a cache size of $1. The default size is processor dependent.

]]> N -Mvect=cachesize:n Instructs the vectorizer to enable loop fusion.

]]> -Mvect=fuse Instructs the vectorizer to disable vectorization of indirect array references.

]]> -Mvect=nogather Instructs the vectorizer to enable idiom recognition.

]]> -Mvect=idiom Instructs the vectorizer to disable idiom recognition.

]]> -Mvect=noidiom Generate vector loops for all loops where possible regardless of the number of statements in the loop. This overrides a heuristic in the vectorizer that ordinarily prevents vectorization of loops with a number of statements that exceed a certain threshold.

]]> -Mvect=nosizelimit Instructs the vectorizer to generate partial vectorization.

]]> -Mvect=partial Instructs the vectorizer to generate prefetch instructions.

]]> -Mvect=prefetch Enables generation of packed SSE instructions for short vector operations that arise from scalar code outside of loops or within the body of a loop iteration.

]]> -Mvect=short Instructs the vectorizer to search for vectorizable loops and, where possible, make use of SSE, SSE2, and prefetch instructions.

]]> -Mvect=sse Instructs the driver to disable the -Mvect=sse option which is part of the "-fast" option.

]]> -Mvect=nosse Enable automatic vector pipelining.

]]> -Mvect Disables -Ktrap=fp.

]]> -Mnofptrap -Ktrap is only processed by the compilers when compiling main functions' programs. The options inv, denorm, divz, ovf, unf, and inexact correspond to the processor's exception mask bits invalid operation, denormalized operand, divide-by-zero, overflow, underflow, and precision, respectively. Normally, the processor's exception mask bits are on (floating-point exceptions are masked the processor recovers from the exceptions and continues). If a floating-point exception occurs and its corresponding mask bit is off (or unmasked ), execution terminates with an arithmetic exception (C's SIGFPE signal). -Ktrap=fp is equivalent to -Ktrap=inv,divz,ovf.

]]> -Ktrap=fp Enable OpenMP directives targeting an NVIDIA GPU.

]]> -mp=gpu Use the -mp option to instruct the compiler to interpret user-inserted OpenMP shared-memory parallel programming directives and generate an executable file which will utilize multiple processors in a shared-memory parallel system. When used strictly as a linker flag, the PGI OpenMP runtime will be linked and users can use the environment variables MP_BIND and MP_BLIST to bind a serial program to a CPU.

]]> -mp (For use only on 64-bit Linux targets) Generate code for the medium memory model in the linux86-64 execution environment. The default small memory model of the linux86-64 environment limits the combined area for a user's object or executable to 1GB, with the Linux kernel managing usage of the second 1GB of address for system routines, shared libraries, stacks, etc. Programs are started at a fixed address, and the program can use a single instruction to make most memory references. The medium memory model allows for larger than 2GB data areas, or .bss sections. Program units compiled using either -mcmodel=medium or -fpic require additional instructions to reference memory. The effect on performance is a function of the data-use of the application. The -mcmodel=medium switch must be used at both compile time and link time to create 64-bit executables. Program units compiled for the default small memory model can be linked into medium memory model executables as long as they are compiled -fpic, or position-independent.

]]> -mcmodel=medium Enable support for 64-bit indexing and single static data objects larger than 2GB in size. This option is default in the presence of -mcmodel=medium. Can be used separately together with the default small memory model for certain 64-bit applications that manage their own memory space.

]]> -Mlarge_arrays Enable optimizations using ANSI C type-based pointer disambiguation.

]]> Set the optimization level to -O

]]> -O A basic block is generated for each C statement. No scheduling is done between statements. No global optimizations are performed.

]]> -O0 Level-one optimization specifies local optimization (-O1). The compiler performs scheduling of basic blocks as well as register allocation. This optimization level is a good choice when the code is very irregular; that is it contains many short statements containing IF statements and the program does not contain loops (DO or DO WHILE statements). For certain types of code, this optimization level may perform better than level-two (-O2) although this case rarely occurs.

The PGI compilers perform many different types of local optimizations, including but not limited to:

Note that this is the default optimiation level when no optimization flags are specified on the compilation command line. ]]> -O1 Level-two optimization (-O2 or -O) specifies global optimization. The -fast option generally will specify global optimization; however, the -fast switch will vary from release to release depending on a reasonable selection of switches for any one particular release. The -O or -O2 level performs all level-one local optimizations as well as global optimizations. Control flow analysis is applied and global registers are allocated for all functions and subroutines. Loop regions are given special consideration. This optimization level is a good choice when the program contains loops, the loops are short, and the structure of the code is regular.

The PGI compilers perform many different types of global optimizations, including but not limited to:

]]> -O2 All level 1 and 2 optimizations are performed. In addition, this level enables more aggressive code hoisting and scalar replacement optimizations that may or may not be profitable.

]]> -O3 Performs all level 1, 2, and 3 optimizations and enables hoisting of guarded invariant floating point expressions.

]]> -O4 Link with static libraries.

]]> Staticily link with the NVIDIA runtime libraries. System libraries may still be dynamically linked.

]]> Link with dynamic libraries.

]]> Print the compiler version.

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